It’s located in the preview scene settings. Thanks.
You have your main mesh that you’re previewing above in the ‘Mesh’ section, but you can choose to add another mesh to preview from the Additional Meshes bit.
You may have saved a collection of different skeletal meshes, for example different components of a character, called ‘MyAdditionalMeshes’ which you could then choose from the ‘Additional Meshes’ drop down menu.
Below that you can specify the specific skeletal mesh from that collection that you want to preview.
Thank you very much. So if I would like to have a character made of different parts like in an rpg, where you have your different armor parts, in casa you would like to change them and preview them with every possible combination you would do it this way, is that right? And, another thing, if you have different skeletal meshes as parts, such as the helmet, the chest. Would they share the same skeleton? And, in that case, should you animate each part individually or is better to use sockets? Thanks.
I believe so, yes 
But I haven’t tried it so if anyone else can jump in here then feel free!
I imagine you would use the same skeleton. or I read on another thread that someone just had one main skeleton and then attached other parts as regular meshes and attached them to the bones.
But in the documentation they describe that if you want to share an animation then they have to have the same skeleton.
I’m not sure if one way is better than the other I’m afraid, these may help you out if you haven’t seen them already.
I guess you could try both ways and see which one feels/works better to you